Method for using hydrophobically associative polymers in preparing cellulosic fiber compositions, and cellulosic fiber compositions incorporating the hydrophobically associative polymers

ABSTRACT

A papermaking method and a composition which utilize, as a drainage aid, a water soluble hydrophobically associative polymer which is a copolymer prepared from monomers which include a hydrophobic ethylenically unsaturated monomer, and one or more of a nonionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer, and an anionic ethylenically unsaturated monomer.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation in part of application Ser.No. 09/455,027.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to using hydrophobically modifiedwater-soluble polymers, also referred to hereinafter as hydrophobicallyassociative polymers or HAPs, in the preparation of cellulosic fibercompositions. The present invention further relates to cellulosic fibercompositions, such as paper and paperboard, which incorporate the HAPs

[0004] 2. Description of Background and Other Information

[0005] The making of cellulosic fiber sheets—particularly paper andpaperboard—includes the following:

[0006] producing an aqueous slurry of cellulosic fiber, which may alsocontain inorganic mineral extenders or pigments;

[0007] depositing this slurry on a moving papermaking wire or fabric;and

[0008] forming a sheet from the solid components of the slurry bydraining the water.

[0009] The foregoing is followed by pressing and drying the sheet tofurther remove water. Organic and inorganic chemicals are often added tothe slurry prior to the sheet forming step to make the papermakingmethod less costly or more rapid, or to attain specific properties inthe final paper product.

[0010] The paper industry continuously strives to improve paper quality,increase productivity, and reduce manufacturing costs. Chemicals areoften added to the fibrous slurry before it reaches the papermaking wireor fabric, to improve the method drainage/dewatering and solidsretention; these chemicals are called drainage and/or retention aids.

[0011] As to drainage/dewatering improvement, drainage or dewatering ofthe fibrous slurry on the papermaking wire or fabric is often thelimiting step in achieving faster method speeds. Improved dewatering canalso result in a dryer sheet in the press and dryer sections, resultingin reduced steam consumption. Yet further, this is the stage in thepapermaking method that determines many sheet final properties.

[0012] With respect to solids retention, papermaking retention aids areused to increase the retention of fine furnish solids in the web duringthe turbulent method of draining and forming the paper web. Withoutadequate retention of the fine solids, they are either lost to themethod effluent or accumulate to high levels in the recirculating whitewater loop, potentially causing deposit buildup and impairing papermachine drainage. Additionally, insufficient retention of the finesolids increases the papermakers' cost due to loss of additives intendedto be adsorbed on the fiber to provide the respective paper opacity,strength, or sizing property.

[0013] High MW water-soluble polymers with either cationic or anioniccharge have traditionally been used as retention and drainage aids.Recent development of inorganic microparticles, known as retention anddrainage aids, in combination with high MW water-soluble polymers, haveshown superior retention and drainge efficacy compared to conventionalhigh MW water-soluble polymers. U.S. Pat. Nos. 4,294,885 and 4,388,150teach the use of starch polymers with colloidal silica. U.S. Pat. No.4,753,710 teaches flocculating the pulp furnish with a high MW cationicflocculant, inducing shear to the flocculated furnish, and thenintroducing bentonite clay to the furnish. U.S. Pat. Nos. 5,274,055 and5,167,766 disclose using chemically crosslinked organic microparticle ormicropolymers as retention and drainage aids in papermaking process.

[0014] Hydropohobically modified water-soluble polymers, also referredto hereinafter as hydrophobically associative polymers or HAPs, areknown to those skilled in the art, for example see the Encyclopedia ofPolymer Science and Engineering, 2^(nd) edition, 17, 772-779. U.S. Pat.Nos. 4,432,881 and 4,861,499 disclose the use of these polymers asthickening agents for paint formulations and for applications in oilrecovery methods, such as drilling mud formulations, fracturing fluids,liquid mobility control agents, friction reducing agents, hydraulicfluids, and lubricants. These patents do not teach or suggest the use ofthe polymers in cellulosic compositions such as paper, or in methods forpreparing these cellulosic compositions.

[0015] U.S. Pat. No. 4,305,860 discloses the preparation of stable,pumpable, solvent-free polyampholyte lattices (colloidal dispersions ofa solid copolymer in water) characterized by their colloidal nature andtheir high solids content and low bulk viscosity. The lattices areprepared by polymerizing about 10 to 30 mole % of at least one cationicmonomer, 5 to 30 mole % of at least one anionic monomer, 15 to 35 mole %of at least one hydrophobic monomer and 5 to 70 mole % of at least onenon-ionic hydrophilic monomer, with the monomer percentages totaling 100mole %, in the presence of water and a free-radical initiator andoptionally a chelating agent. The lattices are taught to be particularlyuseful as pigment retention and drainage aids in the manufacture ofpaper and may be added to the pulp while the latter is in the headbox,beater, hydropulper or stock chest. The high hydrophobic group content(>15 mole %) makes this disclosed polymer insoluble in aqueous solution,which distinguishes itself from the water-soluble HAP polymers disclosedin the present invention.

[0016] EP 0 896 966 A1 discloses the preparation of associative polymersby inverse emulsion procedures utilizing a pendant acrylate hydrophobechain extended with a polyoxyethylene group. The associative acrylicpolymers comprise from 95 to 99.95% moles of at least one monomerselected from neutral ethylene, anionic or cationic monomers, from 0.05to 5% moles of at least one acrylic monomer containing the radical2,4,6-triphenoethyl benzene, and from 0 to 0.2% moles of at least onepolyunsaturated monomer. It is preferred that the associative polymerscontain from 0.5 to 5 molar % of polyoxyethylene 2,4,6-triphenoethylbenzene methacrylate. The polymers may be used in diverse areas, such aspaints, glues and adhesives, construction, textiles and paper. Thecomposition is claimed for use as a thickener, flocculation agent,and/or charge retention agent; no data or further specification isprovided for the utilization.

SUMMARY OF THE INVENTION

[0017] The present invention is directed to a cellulosic fibercomposition, particularly a cellulosic sheet such as paper orpaperboard. The invention is also directed to a method for making thecomposition.

[0018] The present invention relates to a method of making a cellulosicfiber composition that includes adding, to a cellulosic pulp slurry, aHAP and relates to a cellulosic fiber composition including an aqueousslurry of cellulosic pulp and a HAP. The HAP is preferably a copolymerincluding hydrophobic groups that are capable of forming a physicalnetwork structure through hydrophobic association, and has at least onemonomer selected from the group consisting of nonionic ethylenicallyunsaturated monomers, cationic ethylenically unsaturated monomers, oranionic ethylenically unsaturated monomers.

[0019] The HAP is highly associative and forms a network structure inaqueous solution as demonstrated by a tan δ value less than an analogouspolymer without the hydrophobic modification, as determined byviscoelastic characterizations of a 0.5% solution. A significentimprovement in retention and drainage activity is obtained when HAP isapplied to a pulp furnish, and at the same time a satisfactory sheetformation is maintained, which is the unique property that a traditionalflocculant could not achieve. The HAP is usually water soluble.

[0020] The HAP may include at least one hydrophobic ethylenicallyunsaturated monomer present in an amount from about 0.001 mole percentto about 10 mole percent, and at least one monomer selected from anonionic ethylenically unsaturated monomer, a cationic ethylenicallyunsaturated monomer, or an anionic ethylenically unsaturated monomerwith the proviso that the at least one hydrophobic ethylenicallyunsaturated monomer does not contain 2,4,6-triphenoethyl benzene.

[0021] The at least one hydrophobic ethylenically unsaturated monomermay be an ethylenically unsaturated monomer having at least one pendanthydrophobic group of the general structure:

[0022] wherein R₁ is hydrogen or methyl; R₂, when present, is —CH₂—,—C(O)—O—, —O—C(O)—, —C(O)—NR₆—, —NR₆—C(O)—, or —O—; R₃, when present, is—(—CH₂—CHR₁—O—)_(n)—, C₁-C₂₀ alkyl, or C₁-C₂₀ hydroxy alkyl wherein nequals 1 to 40 and R₁ is as decribed above; R₄, when present, is —NR₆—or —N⁺(R₆)₂—; R₅ is the pendant hydrophobic group selected from one ormore of C₄-C₂₀ alkyls, C₄-C₂₀ cycloalkyls, polynuclear aromatichydrocarbon groups, alkaryls wherein alkyl has one or more carbons, orhaloalkyls of four or more carbons; R₆, when present, is hydrogen,methyl, CH₂═CR₁—CH₂—, equivalent to the pendent hydrophobic group R₅ asdescribed above, or a mixture thereof; and Z, present when R₄ is—N⁺(R₆)₂—, is the conjugated base of an acid; with the proviso that R₅is not 2,4,6-triphenoethyl benzene.

[0023] The polynuclear aromatic hydrocarbon group may be naphthyl. Thehaloalkyls of four or more carbons may be perfluoroalkyls whichpreferably are selected from one or more of C₄F₉-C₂₀F₄₁. The pendanthydrophobic group may be polyalkyleneoxy groups wherein the alkylene ispropylene or higher alkylene and there is at least one alkyleneoxy unitper hydrophobic moiety or may be selected from one or more of C₄-C₂₀alkyl groups or preferably from one or more of C₈-C₂₀ alkyl groups.

[0024] Preferably the hydrophobic ethylenically unsaturated monomerdepicted in FIG. 1 may be selected from one or more hydrocarbon estersof ethylenically unsaturated carboxylic acids and their salts, N-alkylethylenically unsaturated amides, α-olefins, vinyl esters, vinyl ethers,N-vinyl amides, alkylstyrenes, alkyl polyethyleneglycol (meth)acrylates,or N-alkyl ethylenically unsaturated cationic monomers. Theethylenically unsaturated carboxylic acids may preferably be selectedfrom the C₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid and morepreferably from dodecyl acrylate or dodecyl methacrylate. Theethylenically unsaturated amides may preferably be selected fromN-octadecyl acrylamide, N-octadecyl methacrylamide, or N,N-dioctylacrylamide. The α-olefins may preferably be selected from 1-octene,1-decene, 1-dodecene, or 1-hexadecene. The vinyl esters may preferablybe vinyl laurate or vinyl stearate. The vinyl alkyl ethers maypreferably be dodecyl vinyl ether or hexadecyl vinyl ether. The N-vinylamides may preferably be N-vinyl lauramide or N-vinyl stearamide. Thealkylstyrene may preferably be t-butyl styrene. The alkylpolyethyleneglycol (meth)acrylates may preferably be selected fromlaurylpolyethoxy(23) methacrylate. The N-alkyl ethylenically unsaturatedcationic monomers may preferably be selected from the C₁₀-C₂₀ alkylhalide quaternary salts of methyldiallyamine,N,N-dimethylaminoalkyl(meth)acrylates, andN,N-dialkylaminoalkyl(meth)acrylamides.

[0025] The at least one nonionic ethylenically unsaturated monomer maybe one or more of acrylamide, methacrylamide, N-alkylacrylamides,N,N-dialkylacrylamides, methyl acrylate, methyl methacrylate,acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinylacetate, or N-vinyl pyrrolidone. The N-alkylacrylamide is preferablyN-methylacrylamide and the N,N-dialkylacrylamide is preferablyN,N-dimethylacrylamide. The at least one nonionic ethylenicallyunsaturated monomer is preferably one or more of acrylamide,methacrylamide, or N-methylacrylamide and more preferably acrylamide.

[0026] The at least one anionic ethylenically unsaturated monomer may beone or more of acrylic acid, methacrylic acid,2-acrylamido-2-methyl-propane sulfonate, sulfoethyl-(meth)acrylate,vinylsulfonic acid, styrene sulfonic acid, maleic acid or the saltsthereof, preferably one or more of acrylic acid, methacrylic acid or thesalts thereof and more preferably one or more of the sodium or ammoniumsalts of acrylic acid.

[0027] The at least one cationic ethylenically unsaturated monomer maybe selected from one or more of diallylamine, the (meth)acrylates ofdialkylaminoalkyl compounds, the (meth)acrylamides of dialkylaminoalkylcompounds, the N-vinylamine hydrolyzate of N-vinylformamide, and thesalts and quaternaries thereof. The quaternary salt of diallylamine maypreferably be diallyldimethylammonium chloride. The dialkylaminoalkyl(meth)acrylamide may preferably be N,N-dimethylaminopropylacrylamide,the acid or quantenary salt thereof may preferably beN,N,N-trimethylaminopropylacrylamide chloride. The dialkylaminoalkyl(meth)acrylate may preferably be N,N-dimethylaminoethylacrylate, theacid or quantenary salt thereof may preferably beN,N,N-trimethylaminoethylacrylate chloride. The at least one cationicethylenically unsaturated monomer may also be selected from one or moreof the compounds of the following general formulae:

[0028] wherein

[0029] R₁ is hydrogen or methyl,

[0030] R₂, R₃, and R₄ are hydrogen, alkyl of C₁ to C₃, or hydroxyethyl,

[0031] R₂ and R₃ or R₂ and R₄ can combined to form a cyclic ringcontaining one of more hetero atoms,

[0032] Z is the conjugate base of an acid,

[0033] X is oxygen or NR₁ wherein R₁ is as defined above, and

[0034] A is an alkylene group of C₁ to C₁₂; or

[0035] wherein

[0036] R₅ and R₆ are hydrogen or methyl,

[0037] R₇ and R₈ are hydrogen, alkyl of C₁ to C₃, or hydroxyethyl; and

[0038] Z is as defined above;

[0039] or N-vinylformamides and the associated hydrolyzates asrepresented by recurring units of

[0040] wherein

[0041] R₁, R₂ and R₃ are each H or C₁ to C₃ alkyl, and

[0042] Z is defined as above.

[0043] It is noted that the description of the hydrophobic ethylenicallyunsaturated monomer encompasses the cationic ethylenically unsaturatedmonomers depicted in FIGS. 2-6 wherein, for example, the definition ofR₂ of FIGS. 2, 4-5 and R₇ of FIG. 3 are substituted with pendanthydrophobic moeity R₅ of FIG. 1.

[0044] It is preferable that HAP in accordance with this invention (an0.5% aqueous solution of the HAP) have a dynamic oscillation frequencysweep tan delta value at 0.0068 Hz less than an analogous polymer absentthe hydrophobic ethylenically unsaturated monomer, most preferably lessthan 1. It is also preferable that the at least one hydrophobicethylenically unsaturated monomer groups be present in an amount fromabout 0.01 mole percent to about 10 mole percent, and more preferably inan amount from about 0.1 mole percent to about 5.0 mole percent.

[0045] The HAP used in this invention may be an anionic, nonionic,cationic or amphoteric copolymer, and preferably an anionic copolymer.The anionic copolymer may include at least one hydrophobic ethylenicallyunsaturated monomer and at least one anionic ethylenically unsaturatedmonomer and may further include at least one nonionic ethylenicallyunsaturated monomer.

[0046] The anionic copolymer may include about 0.001 mole percent toabout 10 mole percent of the at least one hydrophobic ethylenicallyunsaturated monomer, about 1 mole percent to about 99.999 mole percentof the at least one anionic ethylenically unsaturated monomer, and about1 mole percent to about 99.999 mole percent of the at least one nonionicethylenically unsaturated monomer; preferably about 0.01 mole percent toabout 5 mole percent of the at least one hydrophobic ethylenicallyunsaturated monomer, about 10 mole percent to about 90 mole percent ofthe at least one anionic ethylenically unsaturated monomer, and about 10mole percent to about 90 mole percent of the at least one nonionicethylenically unsaturated monomer; and more preferably about 0.1 molepercent to about 2.0 mole percent of the at least one hydrophobicethylenically unsaturated monomer, about 30 mole percent to about 70mole percent of the at least one anionic ethylenically unsaturatedmonomer, and about 50 mole percent to about 70 mole percent of the atleast one nonionic ethylenically unsaturated monomer.

[0047] The inventive cellulosic pulp slurry containing the HAP may alsoinclude, at the option of the skilled worker, other components such asat least one flocculant, at least one starch, at least one inorganic ororganic coagulant, or at least one filler.

[0048] The present invention also includes a cellulosic sheet producedby the inventive method. The cellulosic sheet may include paper andpaperboard incorporating the HAP.

[0049] The present invention also relates to a method of making acellulosic fiber composition which includes adding, to a cellulosic pulpslurry, a HAP and relates to a cellulosic fiber composition including anaqueous slurry of cellulosic pulp and a HAP, where the HAP includes atleast one hydrophobic ethylenically unsaturated monomer present in anamount from about 0.001 mole percent to about 10 mole percent andselected from one or more of C₁₀-C₂₀ alkyl esters of acrylic andmethacrylic acid; and at least one monomer selected from: a) about 1mole percent to about 99.999 mole percent of at least one nonionicethylenically unsaturated monomer selected from one or more ofacrylamide, methacrylamide, N-alkylacrylamides, N,N-dialkylacrylamides,methyl acrylate, methyl methacrylate, acrylonitrile, N-vinylmethylacetamide, N-vinyl methyl formamide, vinyl acetate, or N-vinylpyrrolidone; b) about 1 mole percent to about 99.999 mole percent of atleast one anionic ethylenically unsaturated monomer selected from one ormore of acrylic acid, methylacrylic acid, 2-acrylamido-2-methyl-propanesulfonate, sulfoethyl-(meth)acrylate, vinylsulfonic acid, styrenesulfonic acid, maleic acid or the salts thereof; or c) about 1 molepercent to about 99.999 mole percent of at least one cationicethylenically unsaturated monomer selected from one or more ofdiallylamine, the (meth)acrylates of dialkylaminoalkyl compounds, the(meth)acrylamides of dialkylaminoalkyl compounds, the N-vinylaminehydrolyzate of N-vinylformamide, and the salts and quaternaries thereof.

[0050] The HAP may preferably include at least one hydrophobicethylenically unsaturated monomer present in an amount from about 0.001mole percent to about 10 mole percent and selected from one or more ofC₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid; and at least onemonomer selected from: a) about 1 mole percent to about 99.999 molepercent of at least one nonionic ethylenically unsaturated monomerselected from one or more of acrylamide, methacrylamide, orN-alkylacrylamides; b) about 1 mole percent to about 99.999 mole percentof at least one anionic ethylenically unsaturated monomer selected fromone or more of acrylic acid, methacrylic acid or the salts thereof; orc) about 1 mole percent to about 99.999 mole percent of at least onecationic ethylenically unsaturated monomer selected from one or more ofN,N-dialkylaminoalkyl acrylates, N,N-dialkylaminoalkyl methacrylates,the acid or quaternary salts thereof Preferably, the at least onehydrophobic ethylenically unsaturated monomer may be selected from oneor more of dodecyl acrylate or dodecyl methacrylate, the nonionicethylenically unsaturated monomer may be acrylamide, the at least oneanionic ethylenically unsaturated monomer may be selected from one ormore of the sodium or ammonium salts of acrylic acid, and the cationicethylenically unsaturated monomer may be the methyl chloride quaternaryof N,N-dimethylaminoethylacrylate.

[0051] To the aforementioned pulp slurry containing the HAP may beadded, at the option of the skilled worker, additional components, suchas at least one flocculant, at least one starch, at least one coagulant,or at least one filler.

[0052] The present invention also relates to a method of making acellulosic fiber composition which includes adding, to a cellulosic pulpslurry, an anionic HAP and relates to a cellulosic fiber compositionincluding an aqueous slurry of cellulosic pulp and an anionic HAP, wherethe anionic HAP preferably includes at least one hydrophobicethylenically unsaturated monomer selected from one or more of laurylacrylate or lauryl methacrylate, the at least one nonionic ethylenicallyunsaturated monomer being acrylamide, and the at least one anionicethylenically unsaturated monomer being acrylic acid. To theaforementioned pulp slurry containing the HAP may be added, at theoption of the skilled worker, additional components, such as at leastone flocculant, at least one starch, at least one inorganic or organiccoagulant, or at least one filler. The invention also relates to acellulosic sheet produced by the aforesaid method and from the aforesaidcomposition. The cellulosic sheet may include paper and paperboardincorporating the HAP.

[0053] The cellulosic fiber composition of the invention preferablycomprises the HAP and its viscoelasticity properties, as discussed.Preferred cellulosic fiber compositions of the invention include paper.

DESCRIPTION OF THE INVENTION

[0054] 1. Definitions

[0055] As used herein, the term “HAP” refers to the hydrophobicallyassociative polymer of this invention.

[0056] As used herein, the term “hydrocarbon” includes “aliphatic”,“cycloaliphatic”, and “aromatic”. The terms “aliphatic” and“cycloaliphatic”—unless stated otherwise—are understood as including“alkyl”, “alkenyl”, “alkynyl”, and “cycloalkyl”. The term“aromatic”—also unless stated otherwise—is understood as including“aryl”, “aralkyl”, and “alkaryl”.

[0057] Hydrocarbon groups are understood as including bothnonsubstituted hydrocarbon groups and substituted hydrocarbon groups,with the latter referring to the hydrocarbon portion bearing additionalsubstituents besides the carbon and hydrogen. Correspondingly,aliphatic, cycloaliphatic, and aromatic groups are understood asincluding both nonsubstituted aliphatic, cycloaliphatic, and aromaticgroups and substituted aliphatic, cycloaliphatic, and aromatic groups,with the latter referring to the aliphatic, cycloaliphatic, and aromaticportion bearing additional substituents besides the carbon and hydrogen.

[0058] Also as discussed herein, copolymers are understood as includingpolymers consisting of, or consisting substantially of or consistingessentially of, two different monomeric units. Copolymers are furtherunderstood as including polymers incorporating three or more differentmonomeric units, e.g., terpolymers, etc.

[0059] 2. Method of the Invention

[0060] The invention comprises a method of making cellulosic fibercompositions—particularly cellulosic fiber webs, more particularlycellulosic fiber sheets, and still more particularly paper andpaperboard. This method comprises the addition of at least one HAP to asuitable paper furnish—e.g., a cellulosic fiber pulp or stock,particularly a cellulosic wood fiber pulp or stock.

[0061] Preferably this polymer is added to a slurry comprising anaqueous suspension of the furnish. Also as a matter of preference, acellulosic web—particularly a sheet, and still more particularly paperor paperboard—is formed from the slurry.

[0062] The method of the invention can entail the steps of providing apaper furnish comprised of cellulosic fibers with or without additionalmineral fillers suspended in water, depositing the furnish on apapermaking wire or fabric, and forming a sheet out of the solidcomponents by dewatering the slurry, with the at least one HAP beingadded at one or more points during this method. Preferably, this polymeris introduced into the fibrous slurry prior to the dewatering sequence.

[0063] The HAP serves to provide an increase in retention of fineparticles and/or an increase in fibrous dewatering. This polymer isparticularly effective in providing for retention both of filler—whereit is employed—and of cellulosic fiber fines, these fines beinggenerated from the fiber during the method of the invention. It ispostulated that HAPs form physical network structure through thehydrophobic group in aqueous solution as demonstrated by theirviscoelasticity behavior. Since the three-dimension structure of the HAPis less absorbed on the particle surface, better bridging is providedbetween particles, which leads to better retention and drainageactivity.

[0064] Viscoelastic behavior as discussed herein (Rheology: Principles,Measurements, and Applications, C. W. Macosko, Wiley, New York, N.Y.)denotes a time dependent response to a deformation, i.e., at short timesthe material is hard and glassy, whereas at longer times the material isrubbery or viscous. A common way to measure this phenomenon is by stressrelaxation, where an instantaneous strain is imposed upon a material,and the resultant stress decay over time is recorded. A purely viscousmaterial would exhibit a stress of zero once the strain becomesconstant, while an elastic solid would show no stress decay. Aviscoelastic material would exhibit a stress decay between these twoextremes; thus exhibiting combined elastic and viscous response, orviscoelasticity.

[0065] Dynamic oscillation characterizations are conducted on the HAPmaterials to characterize the viscoelastic properties, wherein a sampleis deformed sinusoidally. The test is conducted via a stress sweep,wherein a constant frequency is applied with an increasing stress(amplitude), or conversely a frequency sweep, wherein a constant stressis applied with varied frequency. The measured strain of the elasticcomponent of the material will be in phase with the imposed stress,whereas the viscous component of the material will be 90ô out of phase.The tan δ is the ratio of the viscous to elastic components of thematerial, and characterizes the material as exhibiting more viscous orelastic properties. Thus, a material having a tan δ of greater than 1 ata specific frequency would exhibit predominantly viscous behavior, and atan δ less than 1 would exhibit predominantly elastic behavior.

[0066] The HAP may be utilized as the sole retention/drainage aid.Alternatively, this polymer may be employed in combination with at leastone flocculant, such as a conventional papermaking flocculent—e.g., ahigh MW cationic, anionic, or nonionic flocculent.

[0067] The method of the invention can be practiced using a papermakingapparatus or system as discussed herein. It is emphasized that theinventive method is not limited to this particular apparatus or system,which is only provided as a representative example of what can beemployed.

[0068] As reviewed in Handbook for Pulp and Paper Technologists (G. A.Smook, TAPPI Press, Atlanta, Ga.), pulp components are usually meteredinto the machine stock chest at a consistency level between 2.8 and 3.2wt %. The machine stock chest will usually contain the final mixture,although in some instances, small concentrations of additives may beadded just prior to the headbox. The machine chest stock is usuallycirculated to a constant head tank (stuff box), which feeds the stockthrough a control valve (the basis weight valve) into the paper machineapproach system.

[0069] The heart of the approach system is the fan pump which serves tomix the stock with the white water and deliver the blend to the headbox.Here the stock is combined with the circulating white water from thewire pit, and the consistency is reduced to the level required at theheadbox (usually between about 0.5 wt % and about 1.0 wt % consistency).

[0070] The white water, which typically has a solids concentration ofabout 0.1 weight percent or less, is liquid from the dewatering of thepulp slurry on the papermaking wire that drains into the wire pit.

[0071] After the fan pump, the pulp slurry typically passes through acentrifugal cleaner, and then through a pressure screen, to a head box.

[0072] The centrifugal cleaner removes debris such as shives andslivers, and the pressure screen removes gross contamination and deflocsthe fibers. The headbox serves to distribute the stock onto the earlierindicated endless moving papermaking wire or fabric; this may be aFourdrinier wire or a twin wire former.

[0073] On the moving papermaking wire or fabric the slurry is dewatered;the resulting liquid is the white water as discussed above, drainingfrom the slurry into the wire pit. This drainage forms the slurry into asheet as it is carried on the wire or fabric to the press section.

[0074] Traveling through the press section, the sheet is pressed betweenrollers and thereby subjected to further dewatering. The sheet continuesthrough the press section into a dryer section, wherein it isadditionally dried. From the dryer section the sheet continues through acalender stack. In the calender stack it is pressed between metalrollers to reduce thickness and smooth the surface.

[0075] From this calender stack the sheet is wound onto a reel.

[0076] The resultant paper may also be surface coated with a sizingagent or coating material.

[0077] The materials utilized in the method of the invention includecellulosic pulp and at least one HAP. There can also be employed one ormore additional materials, including at least one starch, at least onefiller, at least one inorganic or organic coagulant, and at least oneconventional flocculent.

[0078] Where a flocculant is employed, the flocculant and the HAP may beadded simultaneously, or at different points in the method without anintermittent shear point, or at different points with an intermittentshear point between their respective additions. Preferably, theflocculant and the HAP are introduced into the method of the inventionsequentially, i.e., at different points or times. The flocculant may beadded before or after the HAP.

[0079] A shear may be affected to the stock between the addition of theflocculant and HAP when added sequentially. In an apparatus or system asdiscussed herein, high shear is effected at the fan pump, centrifugalcleaner, and pressure.

[0080] Consistent with the foregoing, the apparatus or system preferablyis provided with suitable feed points for adding the previouslydiscussed materials, such as the flocculant and the HAP. In this regard,the flocculant and/or the HAP may be added at a feed point before thefan pump (e.g., between the basis weight valve and the fan pump), and/orat a feed point before the centrifugal cleaner (e.g., between the fanpump and the centrifugal cleaner), and/or at a feed point before thepressure screen (e.g., between the centrifugal cleaner and the pressurescreen).

[0081] With respect to feed points for the other materials, starch,filler, or coagulant may be added at numerous points within the processas is known to those skilled in the art.

[0082] The order in which the different materials are introduced intothe method of the invention is not limited to that set forth in thepreceding discussion, but will generally be based on practicality andperformance for each specific application.

[0083] 3. Materials Employed

[0084] a. Cellulosic Pulp

[0085] Suitable cellulosic fiber pulps for the method of the inventioninclude conventional papermaking stock such as traditional chemicalpulp. For instance, bleached and unbleached sulfate pulp and sulfitepulp, mechanical pulp such as groundwood, thermomechanical pulp,chemi-thermomechanical pulp, recycled pulp such as old corrugatedcontainers, newsprint, office waste, magazine paper and othernon-deinked waste, deinked waste, and mixtures thereof, may be used.

[0086] b. Starch

[0087] Starch adds strength properties, particularly dry strength, tothe cellulosic product obtained from the method of the invention.Particularly, starch increases interfiber bonding in the stock. Starchwill also affect drainage properties.

[0088] Starches that may be used in the method of the invention includecationic and amphoteric starches. Suitable starches include thosederived from corn, potato, wheat, rice, tapioca, and the like.

[0089] Cationicity is imparted by the introduction of cationic groups,and amphotericity by the further introduction of anionic groups. Forinstance, cationic starches may be obtained by reacting starch withtertiary amines or with quaternary ammonium compounds, e.g.,dimethylaminoethanol and 3-chloro-2-hydroxypropyltrimethylammoniumchloride. Cationic starches preferably have a cationic degree ofsubstitution (D.S.)—i.e., the average number of cationic groupssubstituted for hydroxyl groups per anhydroglucose unit—of from about0.01 to about 1.0, more preferably about 0.01 to about 0.10, morepreferably about 0.02 to 0.04.

[0090] Amphoteric starches can be provided by the introduction ofvarious different anionic groups. Preferred amphoteric starches arethose with a net cationicity.

[0091] As an example, anionic phosphate groups can be introduced intocationic starches through reaction with phosphate salts or phosphateetherifying reagents. Where the cationic starch starting material isstarch diethylaminoethyl ether, the amount of phosphate reagent employedin the modification preferably is that which will provide about0.07-0.18 mole of anionic groups per mole of cationic groups.

[0092] Other amphoteric starches that may be used are those made byintroduction of sulfosuccinate groups into cationic starches. Thismodification is accomplished by adding maleic acid half-ester groups toa cationic starch and reacting the maleate double bond with sodiumbisulfite.

[0093] As yet additional examples, cationic starch can be etherifiedwith 3-chloro-2-sulfopropionic acid, carboxyl groups can be introducedinto starches by reaction with sodium chloroacetate or by hypochloriteoxidation, and propane sultone can be employed to treat cationicstarches to provide amphotericity.

[0094] Further useful amphoteric starches can be obtained by xanthationof diethylaminoethyl- and 2-(hydroxypropyl)trimethylammonium starchethers.

[0095] Yet additionally, the modification can be extended by theintroduction of nonionic or hydroxyalkyl groups from treatment withethylene oxide or propylene oxide.

[0096] Starch is preferably employed, in the method of the invention, ina proportion of from about 1 lb. per ton to about 100 lbs. per ton ofcellulosic pulp, based on the dry weight of the pulp. The starchconcentration is more preferably from about 2.5 lbs. per ton to about 50lbs. per ton, and still more preferably from about 5 lbs. per ton toabout 25 lbs. per ton, of the pulp.

[0097] c. Filler

[0098] Filler provides optical properties to the cellulosic product. Itprovides opacity and brightness to the finished sheet, and improves itsprinting properties. Fillers which are suitable include calciumcarbonate (both naturally occurring ground carbonate and syntheticallyproduced precipitated carbonate), titanium oxide, talc, clay, andgypsum. The amount of filler employed can be that which results in acellulosic product of up to about 50 weight percent filler, based on thedry weight of the pulp.

[0099] d. Coagulant

[0100] The coagulant is utilized in addition to the flocculant and HAPto enhance retention and drainage. The employed coagulant may be eitherinorganic or organic.

[0101] The most common inorganic coagulant is an alumina species.Suitable examples include technical grade aluminum sulfate (alum),polyaluminum chloride, polyhydroxy aluminum chloride, polyhydroxyaluminum sulfate, sodium aluminate, and the like.

[0102] The organic coagulant is typically a synthetic, polymericmaterial. Suitable examples include polyamines, poly(amido amines),polyDADMAC, polyethyleneimine, hydrolyzates and quaternized hydrolyzatesof N-vinyl formamide polymers and copolymers, and the like.

[0103] The coagulant is preferably employed, in the method of theinvention, in a proportion of from about 0.05 lb. per ton to about 50lbs. per ton of cellulosic pulp, based on the dry weight of the pulp.The coagulant concentration is more preferably from about 0.5 lbs. perton to about 20 lbs. per ton, and still more preferably from about 1 lb.per ton to about 10 lbs. per ton, of the pulp.

[0104] e. Flocculant

[0105] Ionic flocculants conventional in the papermaking art aresuitable as flocculants for the method of the present invention.Cationic, anionic, nonionic, and amphoteric flocculants—particularly,cationic, anionic, nonionic, and amphoteric polymers—can be used.

[0106] Polymers suitable as flocculants in the method of the inventioninclude homopolymers of a nonionic ethylenically unsaturated monomer.Copolymers of monomers comprising two or more nonionic ethylenicallyunsaturated monomers can also be used, as can copolymers of monomerscomprising at least one nonionic ethylenically unsaturated monomer andat least one cationic ethylenically unsaturated monomer and/or at leastone anionic ethylenically unsaturated monomer.

[0107] The nonionic, cationic, and anionic ethylenically unsaturatedmonomers which may be employed are those discussed herein as beingappropriate for the at least one HAP of the invention.

[0108] Suitable nonionic ethylenically unsaturated monomers includeacrylamide; methacrylamide; N-alkylacrylamides, such asN-methylacrylamide; N,N-dialkylacrylamides, such asN,N-dimethylacrylamide; methyl acrylate; methyl methacrylate;acrylonitrile; N-vinyl methylacetamide; N-vinyl methyl formamide; vinylacetate; N-vinyl pyrrolidone; hydroxyalkyl(meth) acrylates such ashydroxyethyl(meth) acrylate or hydroxypropyl(meth) acrylate; mixtures ofany of the foregoing and the like. Of the foregoing, acrylamide,methacrylamide, and the N-alkylacrylamides are preferred, withacrylamide being particularly preferred.

[0109] Among the cationic ethylenically unsaturated monomers which maybe used are diallylamine, the (meth)acrylates of dialkylaminoalkylcompounds, the (meth)acrylamides of dialkylaminoalkyl compounds, theN-vinylamine hydrolyzate of N-vinylformamide, and the salts andquaternaries thereof. The N,N-dialkylaminoalkyl acrylates andmethacrylates, and their acid and quaternary salts, are preferred, withthe methyl chloride quaternary of N,N-dimethylaminoethylacrylate beingparticularly preferred. Further as to the cationic monomers, suitableexamples include those of the following general formulae:

[0110] where R₁ is hydrogen or methyl, R₂ is hydrogen or lower alkyl ofC₁ to C₄, R₃ and/or R₄ are hydrogen, alkyl of C₁ to C₁₂, aryl, orhydroxyethyl, and R₂ and R₃ or R₂ and R₄ can combine to form a cyclicring containing one of more hetero atoms, Z is the conjugate base of anacid, X is oxygen or NR₁ wherein R₁ is as defined above, and A is analkylene group of C₁ to C,₂; or

[0111] where R₅ and R₆ are hydrogen or methyl, R₇ is hydrogen or alkylof C₁ to C₁₂, and R₈ is hydrogen, alkyl of C₁ to C₁₂, benzyl, orhydroxyethyl; and Z is as defined above; or N-vinylformamides and theassociated hydrolyzates as represented by recurring units of

[0112] where R¹, R² and R³ are each H or C₁ to C₃ alkyl, and Z isdefined above.

[0113] Suitable anionic ethylenically unsaturated monomers includeacrylic acid, methylacrylic acid, and their salts;2-acrylamido-2-methyl-propane sulfonate; sulfoethyl-(meth)acrylate;vinylsulfonic acid; styrene sulfonic acid; and maleic and other dibasicacids and their salts. Acrylic acid, methacrylic acid and their saltsare preferred, with the sodium and ammonium salts of acrylic acid beingparticularly preferred.

[0114] The monomers may be polymerized into polymer by a number ofinitiator systems, including free radical (thermal and redox methods),cationic, and anionic synthesis methods. The flocculant polymer may beprepared by a number of commercial means, including bulk polymerization,solution polymerization, dispersion polymerization, and emulsion/inverseemulsion polymerization. The resultant polymer may be provided to theend use in a number of physical forms, including aqueous solution, drysolid powder, dispersion, and emulsion form.

[0115] The flocculant may be non-ionic, cationic, anionic, oramphoteric. Non-ionic polymer flocculants will contain one or more ofthe previously described non-ionic monomers.

[0116] Cationic polymer flocculants will contain one or more of thecationic monomers described above. The level of total cationic monomer,based upon molar concentrations, will range from about 1 to about 99%,preferably from about 2 to about 50%, and still more preferably fromabout 5 to about 40 mole % cationic monomer, with the remaining monomerbeing one of the previously described non-ionic monomers.

[0117] Anionic polymer flocculants will contain one or more of theanionic monomers described above. The level of total anionic monomer,based upon molar concentrations, will range from about 1 to about 99%,preferably from about 2 to about 50%, and still more preferably fromabout 5 to about 40 mole % cationic monomer, with the remaining monomerbeing one of the previously described non-ionic monomers.

[0118] Amphoteric polymer flocculants will contain a combination of oneor more of the described cationic and anionic monomers. Any combinationof cationic and anionic monomer(s) are preferred, provided at least onecationic and one anionic monomer are utilized. The polymer may containan excess of cationic monomer, an excess of anionic monomer, orequivalent amounts of both cationic and anionic monomers. The level oftotal ionic monomer, being the combined amount of both cationic andanionic monomers, based upon molar concentrations, will range from about1 to about 99%, preferably from about 2 to about 80%, and still morepreferably from about 5 to about 40 mole % cationic monomer, with theremaining monomer being one of the previously described non-ionicmonomers.

[0119] The flocculant is preferably employed, in the method of theinvention, in a proportion of from about 0.01 lb. per ton to about 10lbs. per ton of cellulosic pulp, based upon active polymer weight and onthe dry weight of the pulp. The concentration of flocculant is morepreferably from about 0.05 lb. per ton to about 5 lbs. per ton, andstill more preferably from about 0.1 lb. per ton to about 1 lb. per ton,of the pulp.

[0120] f. Hydrophobically Associative Polymer (HAP)

[0121] The invention comprises at least one HAP. Suitable HAPs of theinvention include copolymers comprising at least one hydrophobicethylenically unsaturated monomer with the proviso that the at least onehydrophobic ethylenically unsaturated monomer does not contain2,4,6-triphenoethyl benzene. These copolymers further include at leastone nonionic ethylenically unsaturated monomer, and/or at least onecationic ethylenically unsaturated monomer, and/or at least one anionicethylenically unsaturated monomer.

[0122] The indicated hydrophobic ethylenically unsaturated monomersinclude water-insoluble hydrophobic ethylenically unsaturated monomers.Further as to the hydrophobic ethylenically unsaturated monomers, theyinclude ethylenically unsaturated monomers, particularly water-insolublemonomers and monomeric surfactants, having hydrophobic groups. Thehydrophobic groups include hydrophobic organic groups, such as thosehaving hydrophobicity comparable to one of the following: aliphatichydrocarbon groups having at least four carbons such as C₄ to C₂₀ alkylsand cycloalkyls; polynuclear aromatic hydrocarbon groups such asbenzyls, substituted benzyls and naphthyls with the proviso that thesubstituted benzyl group is not 2,4,6-triphenoethyl benzene; alkarylswherein alkyl has one or more carbons; haloalkyls of four or morecarbons, preferably perfluoroalkyls; polyalkyleneoxy groups wherein thealkylene is propylene or higher alkylene and there is at least onealkyleneoxy unit per hydrophobic moiety. The preferred hydrophobicgroups include those having at least 4 carbons or more per hydrocarbongroup, such as the C₄-C₂₀ alkyl groups or those having at least 4carbons or more per perfluorocarbon group, such as the C₄F₉-C₂₀F₄₁.Particularly preferred are the C₈-C₂₀ alkyl groups.

[0123] Suitable hydrocarbon group-containing ethylenically unsaturatedmonomers include the esters or amides of the C₄ and higher alkyl groups.

[0124] Particular suitable esters include dodecyl acrylate, dodecylmethacrylate, tridecyl acrylate, tridecyl methacrylate, tetradecylacrylate, tetradecyl methacrylate, octadecyl acrylate, octadecylmethacrylate, nonyl-α-phenyl acrylate, nonyl-α-phenyl methacrylate,dodecyl-α-phenyl acrylate, and dodecyl-α-phenyl methacrylate.

[0125] The C₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid arepreferred. Of these, dodecyl acrylate and methacrylate are particularlypreferred.

[0126] Also the following hydrocarbon group-containing ethylenicallyunsaturated monomers may be used:

[0127] N-alkyl ethylenically unsaturated amides, such as N-octadecylacrylamide, N-octadecyl methacrylamide, N,N-dioctyl acrylamide andsimilar derivatives thereof;

[0128] α-olefins, such as 1-octene, 1-decene, 1-dodecene, and1-hexadecene;

[0129] vinyl esters wherein the ester has at least eight carbons, suchas vinyl laurate and vinyl stearate;

[0130] vinyl ethers, such as dodecyl vinyl ether and hexadecyl vinylether;

[0131] N-vinyl amides, such as N-vinyl lauramide and N-vinyl stearamide;

[0132] -alkylstyrenes, such as t-butyl styrene;

[0133] -alkyl polyethyleneglycol (meth)acrylates such aslaurylpolyethoxy(23) methacrylate; and

[0134] N-alkyl ethylenically unsaturated cationic monomers such as theC₁₀-C₂₀, alkyl halide quaternary salts of methyldiallyamine,N,N-dimethylaminoalkyl(meth)acrylates, andN,N-dialkylaminoalkyl(meth)acrylamides.

[0135] Suitable nonionic ethylenically unsaturated monomers includeacrylamide; methacrylamide; N-alkylacrylamides, such asN-methylacrylamide; N,N-dialkylacrylamides, such asN,N-dimethylacrylamide; methyl acrylate; methyl methacrylate;acrylonitrile; N-vinyl methylacetamide; N-vinyl methyl formamide; vinylacetate; N-vinyl pyrrolidone; mixtures of any of the foregoing and thelike. Of the foregoing, acrylamide, methacrylamide, and theN-alkylacrylamides are preferred, with acrylamide being particularlypreferred.

[0136] Among the cationic ethylenically unsaturated monomers which maybe used are diallylamine, the (meth)acrylates of dialkylaminoalkylcompounds, the (meth)acrylamides of dialkylaminoalkyl compounds, theN-vinylamine hydrolyzate of N-vinylformamide, and the salts andquaternaries thereof. The N,N-dialkylaminoalkyl acrylates andmethacrylates, and their acid and quaternary salts, are preferred, withthe methyl chloride quaternary of N,N-dimethylaminoethylacrylate beingparticularly preferred.

[0137] Further as to the cationic monomers, suitable examples includethose of the following general formulae:

[0138] where R₁ is hydrogen or methyl; R₂, R₃ and R₄ are hydrogen, alkylof C₁ to C₃, or hydroxyethyl; and R₂ and R₃ or R₂ and R₄ can combined toform a cyclic ring containing one or more hetero atoms; Z is theconjugate base of an acid;, X is oxygen or NR₁ wherein R₁ is as definedabove; and A is an alkylene group of C₁ to C₁₂; or

[0139] where R₅ and R₆ are hydrogen or methyl, R₇ and R₈ are hydrogen,alkyl of C₁ to C₃, or hydroxyethyl; and Z is as defined above; orN-vinylformamides and the associated hydrolyzates as represented byrecurring units of

[0140] where R¹, R² and R³ are each H or C₁ to C₃ alkyl, and Z isdefined above.

[0141] Suitable anionic ethylenically unsaturated monomers includeacrylic acid, methylacrylic acid, and their salts;2-acrylamido-2-methyl-propane sulfonate; sulfoethyl-(meth)acrylate;vinylsulfonic acid; styrene sulfonic acid; and maleic and other dibasicacids and their salts. Acrylic acid, methacrylic acid and their saltsare preferred, with the sodium and ammonium salts of acrylic acid beingparticularly preferred.

[0142] As a matter of preference, the proportion of hydrophobicethylenically unsaturated monomer in the HAP is within a range whichrenders the polymer hydrophobically associative—i.e., the hydrophobicmonomer concentration is low enough so that the polymer is still watersoluble or dispersible, but sufficient to provide the associativeproperty as discussed herein. In this regard, the at least one HAPpreferably comprises about 0.001 mole percent to about 10 molepercent—more preferably about 0.01 mole percent to about 5 mole percent,and still more preferably about 0.1 mole percent to about 2.0 molepercent—of the at least one hydrophobic ethylenically unsaturatedmonomer.

[0143] The HAPs used in the invention include anionic, nonionic, andcationic and amphoteric copolymers. Of these, the anionic copolymers arepreferred.

[0144] The anionic copolymers comprise at least one hydrophobicethylenically unsaturated monomer and at least one anionic ethylenicallyunsaturated monomer. Preferably, the anionic copolymers further compriseat least one nonionic ethylenically unsaturated monomer. Particularlypreferred are the terpolymers consisting of, or consisting essentiallyof, or substantially of, at least one hydrophobic ethylenicallyunsaturated monomer, at least one anionic ethylenically unsaturatedmonomer, and at least one nonionic ethylenically unsaturated monomer.

[0145] For the anionic copolymers the preferred hydrophobicethylenically unsaturated monomers are the hydrocarbon esters ofα,β-ethylenically unsaturated carboxylic acids and their salts, withdodecyl acrylate and dodecyl methacrylate being particularly preferred.Preferred nonionic ethylenically unsaturated monomers are acrylamide andmethacrylamide. Preferred anionic ethylenically unsaturated monomers areacrylic acid and methacrylic acid.

[0146] The anionic copolymers preferably comprise about 0.001 molepercent to about 10 mole percent hydrophobic ethylenically unsaturatedmonomer, about 1 mole percent to about 99.999 mole percent nonionicethylenically unsaturated monomer, and about 1 mole percent to about99.999 mole percent of the at least one anionic ethylenicallyunsaturated monomer. More preferably, they comprise about 0.01 molepercent to about 5 mole percent of the at least one hydrophobicethylenically unsaturated monomer, about 10 mole percent to about 90mole percent of the at least one nonionic ethylenically unsaturatedmonomer, and about 10 mole percent to about 90 mole percent of the atleast one anionic ethylenically unsaturated monomer. Still morepreferably, they comprise about 0.1 mole percent to about 2.0 molepercent of the at least one hydrophobic ethylenically unsaturatedmonomer, about 50 mole percent to about 70 mole percent of the at leastone nonionic ethylenically unsaturated monomer, and about 30 molepercent to about 70 mole percent of the at least one anionicethylenically unsaturated monomer.

[0147] The monomers may be polymerized into a HAP polymer by a number ofinitiator systems, including free radical (thermal and redox methods),cationic, and anionic synthesis methods. The HAP may be prepared by anumber of commercial means, including bulk polymerization, solutionpolymerization, micellar solution polymerization, dispersionpolymerization, and emulsion/inverse emulsion polymerization. Theresultant polymer may be provided to the end use in a number of physicalforms, including aqueous solution, dry solid powder, dispersion, andemulsion form.

[0148] The HAP is preferably employed, in the method of the invention,in a proportion of from about 0.01 lb. per ton to about 10 lbs. per tonof cellulosic pulp, based on the dry weight of the pulp. Theconcentration of HAP is more preferably from about 0.05 lb. per ton toabout 5 lbs. per ton, and still more preferably from about 0.1 lb. perton to about 1 lb. per ton, of the pulp.

[0149] g. Further Additives

[0150] The method of the invention may yet additionally includeconventional additives employed in their usual amounts for their usualpurposes. Suitable examples include sizing, promoters, strength agents,dye fixatives, polymeric coagulants, and the like. The produced papermay also be surface treated with a surface size or coating material.

[0151] 4. Composition of the Invention

[0152] A factor affecting the concentration of HAP in the cellulosiccomposition of the invention is the proportion of the polymer addedduring the preparation method. The cellulosic composition of theinvention—which preferably is a cellulosic sheet, and more preferably ispaperboard or paper—preferably comprises about 0.01 to about 10 weightpercent—more preferably about 0.05 weight percent to about 5 weightpercent, and still more preferably about 0.1 weight percent to about 1weight percent—of the HAP, based on the dry weight of the composition.

EXPERIMENTAL SECTION

[0153] The invention is illustrated by the following procedures andtests; these are provided for the purpose of representation, and are notto be construed as limiting the scope of the invention. Unless statedotherwise, all percentages, parts, etc. are by weight.

[0154] 1. Preparation of the Flocculant HAPs of the Invention andControls

[0155] a.) Solution Polymerization

[0156] HAPs used in the invention, the anionic copolymers II, III, and Vto VII are prepared from acrylamide (AM), acrylic acid (AA), and laurylacrylate (LA). Control polymers, the anionic copolymers I and IV, areprepared without the hydrophobically modified monomer laurylacrylate—i.e., from acrylamide and acrylic acid alone.

[0157] Polymers I-VII are all prepared by solution polymerization. Therelative proportions of monomers used in each instance are set forthbelow. TABLE I Solution Polymer Sample Description Polymer Monomers FeedRatio (mole %) I (control) AA/AM 45/55 II AA/AM/LA 45/54/1 III AA/AM/LA45/54/1 IV (control) AA/AM 30/70 V AA/AM/LA 30/69.5/0.5 VI AA/AM/LA30/69/1 VII AA/AM/LA 30/68/2

[0158] In the case of Polymers II and III, a solution of 2.75 parts ofacrylamide, 0.17 parts (1 mol % of the monomers) of lauryl acrylate,2.25 parts of acrylic acid, 1 part of the nonionic surfactant (Tergitol15-S-9), and 100 parts of deionized water is deoxygenated under stirringat room temperature by sparging with nitrogen for 45 minutes. 0.5 partof a 2 mg KBrO₃ solution is added and 10 parts of 0.03% of NaS₂O₅ isinjected by a syringe pump over 60 minutes. The copolymer is obtained bythe precipitation of the polymerization solution in acetone and driedunder vacuum at 50° C. overnight.

[0159] Polymers V, VI and VII are prepared in the same manner, exceptfor the ratio of the monomers. For Polymer V, the monomer ratio is 3.4parts of acrylamide, 0.1 part (0.5 mol % of the monomers) of laurylacrylate, and 1.5 parts of acrylic acid. For Polymer VI, the monomerratio is 3.4 parts of acrylamide, 0.19 parts (1 mol % of the monomers)of lauryl acrylate, and 1.5 parts of acrylic acid. For Polymer VII, themonomer ratio is 3.4 parts of acrylamide, 0.38 parts (2 mol % of themonomers) of lauryl acrylate, and 1.5 parts of acrylic acid.

[0160] Polymer I is prepared using the same method and proportions aswith Polymers II and III, except without the lauryl acrylate. Polymer IVis prepared in the same manner as Polymer I, except that for Polymer IVthe monomer ratio is 3.5 parts of acrylamide and 1.5 parts of acrylicacid.

[0161] For each of Polymers I, II, and III, the resulting dried productis redissolved in deionized water to produce a 0.5% polymer solutionwhich is subjected to viscosity characterization.

[0162] b). Dispersion Polymerization

[0163] Hydrophobic associative polymers are prepared via dispersionpolymerization. TABLE 2 Brine Dispersion Sample Description Feed RatioPolymer Monomer (mole %) VIII (control) AA/AM 50/50 IX AA/AM/LMA49.9/50/0.1 X AA/AM/LMA 49.8/50/0.2 XI AA/AM/LA 50/49.75/0.25 XIIAA/AM/LA 50/49.5/0.5

[0164] 2. Viscosity Characterization

[0165] a). Solution Polymerization

[0166] The viscosity of each 0.5% solution is measured by Brookfieldviscometer at 12 rpm and room temperature. The results are set forth inTable 3 below. The molecular weights of the HAPs II and III, and of thenon-associative Polymer I, are assumed to be similar, because of theirbeing prepared under substantially identical synthesis conditions. The20 fold increase in 0.5% solution viscosity of the HAPs II and III overthe Polymer I control sample is a qualitative indication of theincorporation of the hydrophobic monomer in Polymers II and III. Theextremely high 0.5% solution viscosity for Polymers II and III alsoindicates that the HAPs of the invention are strongly associative inaqueous solution. TABLE 3 Viscosity Characterization Samples Monomers0.5% Solution Viscosity (cP) I (control) AA/AM 600 II AA/AM/LA 14,000III AA/AM/LA 12,000

[0167] Viscosity and rheological characterizations are further conductedon Samples IV through VII to demonstrate the associative properties ofthe modified samples compared to the unmodified control. The describedstudies are conducted at 0.5% aqueous solution. As is exhibitedpreviously in Table 3, Brookfield viscosity at 12 rpm is conducted onthe samples, exhibiting a significant increase in apparent viscositywith increased levels of hydrophobe. The highest level of hydrophobeexhibits a 10 fold increase in Brookfield Viscosity due to associativeinteractions. Additional studies are also conducted with a Haake RS-75controlled stress rheometer equipped with a cone and plate geometry,with a 60 mm diameter cone and a fixed angle of 2 degrees. The apparentviscosity of the 0.5% solid content polymer samples is determined at aconstant shear rate of 10 sec⁻¹, with similar results observed as withthe Brookfield viscometer, in that a 10 fold increase in viscosity isobserved with the highest level of hydrophobe, indicating strongassociative behavior. A stress sweep is conducted with the instrument indynamic stress oscillation mode, at a constant 1 Hz frequency, and astress range of 0.1 to 10.0 Pa in 20 logarithmic steps. The G′ storagemodulus is assigned as the equilibrium value in the linear viscoelasticregion, and is defined as:

G′=(τ₀/γ₀) cos δ

[0168] where τ₀ is the stress amplitude, γ₀ is the maximum strainamplitude, and δ is the phase angle shift between the stress andresultant strain. The G′ storage modulus is also referred to as the gelmodulus, and is taken as an indication of the degree and strength of thenetwork structure, as determined by the inter-/intra-molecularhydrophobic associations. At equivalent applied stress, materials with ahigher G′ value will strain or deform less, thus exhibiting a strongergel complex or network structure. The data demonstrates a linearrelationship between hydrophobe concentration and G′ storage modulus,with the modulus increasing with increased level of hydrophobe, and thehighest G′ storage modulus for the highest level of hydrophobicsubstitution. The unmodified Polymer IV exhibits a storage modulus of 2Pa, while the modified Polymer VII containing 2 mole % lauryl acrylateexhibits a storage modulus of 25.6 Pa.

[0169] A frequency sweep in dynamic oscillation mode is subsequentlyconducted with the instrument in dynamic oscillation mode, at a constantstress of 0.1 Pa, and a frequency range of 0.0068 Hz to 10 Hz with 3readings per frequency decade. The tan δ is the ratio of the loss(viscous) modulus to storage (elastic) modulus, determined according to:

tan δ=loss modulus/storage modulus=G″/G′

[0170] Materials that possess a higher tan δ value exhibit more viscousproperties, while a lower tan δ will indicate more elastic properties.At a low frequency such as 0.0068 Hz, the rate of stress on the samplewill permit a linear polymer to relax, and exhibit a viscous typeresponse, or a higher tan δ. Polymers comprised either of a chemical orphysical network exhibit significant structure of the polymer chains.These network structured materials are mechanically stable and do notrelax within the time frame or frequency of the experiment. Thesematerials exhibit lower values of tan δ, and thus are more elastic. Asshown in Table 4, a tan δ at 0.0068 Hz of 20 is observed for theunmodified control polymer, while the highest level of hydrophobeprovides a tan δ of 0.224. Lower levels of tan δ are observed withhigher levels of hydrophobic substitution over a wide range offrequencies, up to 6.8 Hz. This clearly demonstrates the strongassociative behavior of the HAP, and it is consistent with the viscositydata discussed above. TABLE 4 Controlled Stress Rheometer DynamicOscillation Studies Shear Stress Brook- rate = Sweep Fre- field 10 sec-1G″ quency Feed rpm 0.5% Storage Sweep Ratio 0.5% soln Modu- tan δ, Poly-(mole soln vis, vis, lus, 0068 mer Mononer %) mPas mPAS Pa Hz IV AA/AM30/70 650 1070 2 19.9 (control) V AA/AM/LA 30/69.5/ 1700 2350 2.3 1.10.5 VI AA/AM/LA 30/69/1 8500 16400 12 0363 VII AA/AM/LA 30/68/2 700010500 25.6 0.224

[0171] b). Dispersion Polymerization

[0172] The dispersion polymers are characterized according to equivalentmethods as described in the solution polymerization polymers. The datapresented in Table 5 demonstrates similar results as with the solutionpolymerization products. The 0.5% solution apparent viscosity isobserved to increase with the introduction of the hydrophobic monomer. Astress sweep study in dynamic oscillation mode demonstrates a G′ storagemodulus increase with samples IX and XI compared to the unmodifiedcontrol sample VIII. A frequency sweep study in dynamic oscillation modedemonstrates a low tan δ for the hydrophobic associative polymercompared to the unmodified control. TABLE 5 Controlled Stress RheometerDynamic Oscillation Studies Shear Stress rate = Sweep Fre- 10 sec-1 G′quency Feed 0.5% Storage Sweep Ratio Charge soln Modu- tan δ Poly- (moleDensity vis, lus .0068 mer Monomer %) meq/g mPas Pa Hz VIII AM/AA 50/506.4 530 3.39 7.23 (control) IX AM/AA/ 50/49.9/ 7.5 1230 10.9 0.92 LMA0.1 X AM/AA/ 50/49.8/ 7.0 510 Non- n/a LMA 0.2 linear XI AA/AM/LA 50/7.6 1270 10.9 0.72 49.75/ 0.25 XII AA/AM/LA 50/49.5/ 7.3 410 Non- n/a0.5 linear

[0173] The dilute solution viscosity properties of the Table 5 HAPsamples were determined in aqueous solutions at various concentrationsof NaCl and compared to Polyflex CP.3, a commercial polyacrylamidedrainage aid (Cytec Industries, Inc., West Patterson, N.J.) and PolymerE, a commercial high MW anionic polyacrylamide flocculent. The data arepresented in Table 5.1. As discussed in Introduction to Physical PolymerScience by L. H. Sperling (Wiley Interscience, 1992), the dilutesolution properties provide a relative indication of polymer molecularweight. In this experiment, the solvent viscosity η₀ is compared to thepolymer solution viscosity η. The relative viscosity is the unitlessratio of the two:

η_(rel)=η/η₀

[0174] and the specific viscosity is relative viscosity minus one:

η_(sp)=η_(rel)−1

[0175] The reduced specific viscosity, referred to hereafter as the RSV,is the specific viscosity divided by the polymer concentration (C) ingram per deciliter units:

RSV=η _(sp) /C

[0176] The units for RSV are deciliter per gram (dL/g), and as suchdescribe the hydrodynamic volume (HDV) of a polymer in solution. Thus ahigher RSV indicates a large HDV in solution, and a higher MW whencomparing conventional polymers. The experiment is conducted in thedilute regime such that no polymer coil overlap is occurring. The RSVvalues can be determined by capillary or rotational viscometer methodsby measuring the respective efflux time or apparent viscosity of boththe solvent and the polymer solutions. The data described in Table 5.1were determined with a Brookfield rotational viscometer equipped with anultra-low (UL) adapter, capable of determining the viscosity of lowviscosity solutions. The data demonstrate the effect on polyelectrolyteRSV with varying salt concentrations, as is well known to those skilledin the art. The inventive HAP products demonstrate a higher RSV in 1 MNaCl that contains an additional 0.1% nonylphenol ethoxylate (NPE)surfactant than in 1 M NaCl only. This phenomena, which shall bereferred to as “RSV Ratio”, is a dilute solution property specific toassociative polymers containing hydrophobes, and does not occur inlinear, cross-linked, or branched polymers. The RSV Ratio is observed toincrease dramatically with higher levels of hydrophobic monomer, anddoes not occur in the control polymer, Polyflex CP.3, or Polymer E. Thisphenomena is well established in the literature, and is explained as abinding of the hydrophobic domains with the surfactant, thus providingan increase in dilute solution viscosity or RSV. TABLE 5.1 DiluteSolution RSV Determinations RSV - 1M Ratio - 1M RSV - DI RSV - 0.01MRSV - 1M NaCl + NaCl: 1M Feed Ratio Water NaCl - NaCl - 0.1% NaCl +Polymer Monomer (mole %) dL/g dL/g dL/g NPE 0.1% NPE VIII (control)AM/AA 50/50 730 113 21 23 1.1 IX AM/AA/LMA 50/49.9/0.1 990 106 12 20 1.7X AM/AA/LMA 50/49.8/0.2 700 23 2 15 1.5 XI AA/AM/LA 50/49.75/0.25 930128 16 24 7.5 XII AA/AM/LA 50/49.5/0.5 650 34 4 17 4 3 Polyflex CP.3AM/AA/** 40/60/** 580 47 13 13 1.0 Polymer E AM/AA 50/50 1216 184 44 441 0 [Polymer dL/g .001 .005 .025 .025 Concentration}

[0177] 3. Retention and Drainage Tests

[0178] A first series of Britt jar retention tests and Canadian StandardFreeness (CSF) drainage tests are conducted to compare the performanceof the HAPs of the invention, with those of the following: anon-hydrophobic associative polymer; a conventional anionicpolyacrylamide flocculant; and inorganic and organic drainage aidscommonly referred to within the industry as “microparticles” or“micropolymers”.

[0179] The Britt jar (Paper Research Materials, Inc., Gig Harbor, Wash.)retention test is known in the art. In the Britt jar retention test aspecific volume of furnish is mixed under dynamic conditions and analiquot of the furnish is drained through the bottom screen of the jar,so that the level of fine materials which are retained can bequantified. The Britt jar utilized for the present tests is equippedwith 3 vanes on the cylinder walls to induce turbulent mix, and a 76μscreen in the bottom plate is utilized.

[0180] The CSF device (Lorentzen & Wettre, Code 30, Stockholm, Sweden)utilized to determine relative drainage rate or dewatering rate also isknown in the art (TAPPI Test Procedure T-227). The CSF device comprisesa drainage chamber and a rate measuring funnel, both mounted on asuitable support. The drainage chamber is cylindrical, fitted with aperforated screen plate and a hinged plate on the bottom, and with avacuum tight hinged lid on the top. The rate measuring funnel isequipped with a bottom orifice and a side, overflow orifice.

[0181] The CSF test is conducted by placing 1 liter of furnish,typically at 0.30% consistency, in the drainage chamber, closing the toplid, and then immediately opening the bottom plate. The water is allowedto drain freely into the rate measuring funnel; water flow which exceedsthat determined by the bottom orifice will overflow through the sideorifice and is collected in a graduated cylinder. The values generatedare described in millimeters (mls) of filtrate; higher quantitativevalues represent higher levels of dewatering.

[0182] The furnish employed in this first series of tests is a syntheticalkaline furnish. This furnish is prepared from hardwood and softwooddried market lap pulps, and from water and further materials. First thehardwood and softwood dried market lap pulp are separately refined in alaboratory Valley Beater (Voith, Appleton, Wis.) These pulps are thenadded to an aqueous medium.

[0183] The aqueous medium utilized in preparing the furnish comprises amixture of local hard water and deionized water to a representativehardness. Inorganic salts are added in amounts so as to provide thismedium with a representative alkalinity and a total conductivity.

[0184] To prepare the furnish, the hardwood and softwood are dispersedinto the aqueous medium at typical weight ratios of hardwood andsoftwood. Precipitated calcium carbonate (PCC) is introduced into thefurnish at 25 weight percent, based on the combined dry weight of thepulps, so as to provide a final finish comprising 80% fiber and 20% PCCfiller.

[0185] This first series of tests is conducted with the following:Polymer II, a hydrophobically associative anionic polyacrylamide of theinvention as discussed herein; Polymer I, an unmodified anionicpolyacrylamide control polymer as discussed herein; Polymer E, a high MWcommercial anionic flocculant; Polyflex CP.3, a commercialpolyacrylamide drainage aid (Cytec Industries, Inc., West Patterson,N.J.); and bentonite clay, also commonly employed in the industry as adrainage and retention aid.

[0186] The Britt jar retention tests in this first series are conductedwith 500 mls of the synthetic furnish, having a typical solidsconcentration of 0.5%. The test is conducted at a constant rpm speedaccording to the following parameters, consistent with the sequence setforth in Table 2: add starch, mix; add alum, mix; add polymerflocculant, mix; add drainage aid, mix; obtain filtrate.

[0187] The cationic potato starch utilized is Stalok 600 (A. E. Staley,Decatur, Ill.), and the alum is aluminum sulfate-octadecahydrateavailable as a 50% solution (Delta Chemical Corporation, Baltimore,Md.). The cationic flocculant utilized, referred to as CPAM-P, is a90/10 mole % acrylamide/N,N-dimethylaminoethylacrylate methyl chloridequaternized; this material is commercially available as a self-invertingwater-in-oil emulsion.

[0188] The retention values reported in Table 2 are fines retentionwhere the total fines in the furnish is first determined by washing” 500mls of furnish with 10 liters of water under mixing conditions to removeall the fine particles, defined as particles smaller than the Britt jar76μ screen. The fines retention for each treatment is then determined bydraining 100 mls of filtrate after the described addition sequence, thenfiltering the filtrate through a pre-weighed 1.5μ filter paper. Thefines retention are calculated according to the following equation:

% Fines retention=(filtrate wt ¥ _(i)minus) fines wt)/filtrate wt

[0189] where the filtrate and fines weight are both normalized to 100mls. Retention values represent the average of 2 replicate runs.

[0190] The CSF drainage tests are conducted with 1 liter of the furnishat a solids concentration of 0.30%. The furnish is prepared for thedescribed treatment externally from the CSF device, utilizing equivalentspeeds and mixing times as described for the Britt jar tests, in asquare beaker to provide turbulent mixing. Upon completion of theaddition of the additives and the mixing sequence, the treated furnishis poured into the top of the CSF device and the test is conducted.

[0191] In both Britt jar retention and CSF drainage tests, higherquantitative values indicate higher activity and a more desiredresponse.

[0192] The data set forth in Table 6 illustrates the superior activityprovided by Polymer II of the invention, as compared to the resultsobtained with unmodified control Polymer I and the conventional anionicflocculant Polymer E. Further, the polymer of the invention providesactivity equivalent to that of bentonite clay and approaching that ofPolyflex CP.3. The described material dosages are all based upon productactives, unless noted otherwise. TABLE 6 lbs./ton lbs./ton lbs./tonLbs./ton Avg. CSF ADD #1 (active) ADD #2 (active) Polymer (active)Drainage Aid (active) % Ret mls Cationic Potato Starch 10 Alum 5 none 2729 395 Cationic Potato Starch 10 alum 5 CPAM-P Flocculant 0 5 none 0 4843 380 Cationic Potato Starch 10 alum 5 CPAM-P Flocculant 0 5 Polymer II0 75 69 54 620 Cationic Potato Starch 10 alum 5 CPAM-P Flocculant 0 5Polymer I 0 75 50 46 535 Cationic Potato Starch 10 alum 5 CPAM-PFlocculant 0 5 Polymer E 0 75 53 16 540 Cationic Potato Starch 10 alum 5CPAM-P Flocculant 0.5 Polyflex CP.3 0 75 77 85 650 Cationic PotatoStarch 10 alum 5 CPAM-P Flocculant 0.5 Bentolite HS 4 64 72 600

[0193] A series of retention and drainage tests are conducted utilizinga pulsed drainage device (PDD). The test substrate, test conditions, andassociated chemical additives are identical to those utilized in Table6.

[0194] The PDD is equipped with a rotating hydrofoil, and vacuumcapability underneath a wire screen. It is an instrument developedinternally (described in U.S. Pat. No. 5,314,581) as a reasonablesimulation of the actual retention, drainage, and sheet formationoperations. During the operation of the experiment, a vacuum is appliedto the fibrous slurry to assist in the formation of a fibrous mat, andthe vacuum is continued until a steady state equilibrium vacuum isachieved.

[0195] A variety of measurements can be taken with use of the PDD. Forinstance, the PDD can be used in determining first pass retention, peakvacuum, equilibrium vacuum, peak to equilibrium vacuum ratio (PEVR), andvacuum drainage time.

[0196] The first pass fines retention is determined by mass balancecalculations involving the weight of the final sheet, the total massintroduced into the PDD, and the total fines fraction of the stock whichis defined as the fraction of the stock that has a particle size lessthan 76μ. As with Britt jar fines retention, higher values indicate thedesired response.

[0197] The peak vacuum is the total vacuum required during mat formationuntil air is drawn through the formed mat and the vacuum is disrupted.Equilibrium vacuum is the steady state vacuum drawn through the formedsheet. Both peak vacuum and equilibrium vacuum are measured in inches ofHg. A lower quantitative value for the peak vacuum indicates a fibrousmatrix that is easier to dewater.

[0198] The peak to equilibrium vacuum ratio (PEVR) is the unitless ratioof these two outputs. Studies have demonstrated that this parameter isuseful as an indication of sheet formation, in that lower PEVR valuesindicate more desirable or more uniform sheet formation.

[0199] The vacuum drainage time is the time to peak vacuum, and ismeasured by the instrument in time units of seconds. It is believed thisresponse is similar to the wet-line on a paper machine, which is thepoint where the water has drained sufficiently such that the sheet haslost its sheen or visible free water. The wet line position is commonlymonitored as an indication of papermachine drainage. The desiredresponses for the vacuum drainage parameters are reduced (low) values,indicating improved drainage.

[0200] The second series of drainage tests, utilizing the PDD, is takenwith the same drainage aids as the first series, except for the absenceof bentonite. The associated starch, alum, and cationic flocculant areas described previously. The results in Table 7 set forth the valuesobtained for the above measurements from taking the PDD measurements.

[0201] These results demonstrate that Polymer II of the inventionprovides a definitive drainage dosage response. Specifically, as thedosage is increased, the gravity drainage, the peak vacuum, and thevacuum drainage times improve accordingly.

[0202] It is noted that unmodified control Polymer I and theconventional flocculant Polymer E do not exhibit a dosage response. Inthis regard, as the dosage of these polymers is increased, the retentionand associated drainage responses do not increase or decrease.

[0203] The improved drainage activity of Polymer II, as compared to thatof control Polymer I and Polymer E, is also clearly shown by the Table 7data. Polymer II provides higher fines retention than Polyflex CP.3 andapproaches the drainage activity of Polyflex CP.3, as 1.0 lb./ton ofPolymer II provides about equal drainage to 0.5 lbs./ton of PolyflexCP.3. It is noted that at these equal drainage times, the Polymer IIprovides lower PEVR values than Polyflex CP.3, an indication of improvedsheet uniformity or formation. TABLE 7 10 Lbs./Ton Cationic PotatoVacuum Starch + 5 Lbs./Ton Aluminum % First Gravity Drainage DrainageSulfate + 0.5 Lbs./Ton Pass Time - seconds VACUUM PEAK Peak to Time-seconds CPAM-P Flocculant + DOSAGE Fines (mass Equilibrium. VACUUMEquilibrium (Vacuum Drainage Aid (Lbs./T) Retention measurement) (in Hg)(in Hg) Vacuum Ratio Time) No Drainage Aid 0 89.09% 3.25 3.61 5.15 1.431.028 Polyflex CP.3 0.5 93.47% 3.04 2.97 4.44 1.49 0.679 Polyflex CP.30.75 95.10% 2.99 2.71 4.07 1.50 0.622 Polyflex CP.3 1 95.37% 3.01 2.654.01 1.51 0.608 Polymer I 0.5 92.34% 3.16 3.53 4.88 1.38 0.798 Polymer I0.75 91.34% 3.18 3.53 4.81 1.36 0.801 Polymer I 1 94.74% 3.13 3.52 4.811.37 0.778 Polymer II 0.5 96.05% 3.09 3.27 4.66 1.42 0.731 Polymer II0.75 95.83% 3.05 3.10 4.53 1.46 0.685 Polymer II 1 95.64% 2.91 3.01 4.431.47 0.673 Polymer E 0.5 93.31% 3.14 3.50 4.81 1.37 0.793 Polymer E 0.7592.20% 3.18 3.43 4.78 1.39 0.786 Polymer E 1 94.21% 4.67 3.43 4.83 1.410.792

[0204] A series of Britt jar retention and CSF tests is conducted withthe following: Polymer III, hydrophobically associative anionicpolyacrylamide of the invention as discussed herein; Polymers V-VII,hydrophobically associative polymers of the invention, exhibitingsequentially increased levels of hydrophobic modification; Polymer IV,an unmodified anionic polyacrylamide control polymer as discussedherein; Polymer E; and Polyflex CP.3. The tests are conducted accordingto the methods previously described. The data demonstrates the superioractivity of the invention provided by Polymer III and Polymer VII,compared to the unmodified control Polymer IV. Increased retention anddrainage activity are observed with increased level of hydrophobicsubstitution, with Polymer VII approaching the activity of PolyflexCP.3. The data is set forth in Table 8. TABLE 8 lbs./ton lbs./tonlbs./ton Drainage lbs./ton Avg. Add #1 (active) Add #2 (active) Add #3(active) Aid (active) Ret. CSF Cationic 10 Alum 5 CPAM-P 0.5 some 0  51.4 100 Potato Flocculant Starch Cationic 10 Alum 5 CPAM-P 0.5 PolyflexCP.3 0.75 77.5 510 Potato Flocculant Starch Cationic 10 Alum 5 CPAM-P0.5 Polymer E 0.75 19.5 530 Potato Flocculant Starch Cationic 10 Alum 5CPAM-P 0.5 Polymer IV 0.75 12.0 510 Potato Flocculant Starch Cationic 10Alum 5 CPAM-P 0.5 Polymer V 0.75 12.1 505 Potato Flocculant StarchCationic 10 Alum 5 CPAM-P 0.5 Polymer VI 0.75 55.4 515 Potato FlocculantStarch Cationic 10 Alum 5 CPAM-P 0.5 Polymer VII 0.75 66.3 585 PotatoFlocculant Starch Cationic 10 Alum 5 CPAM-P 0.5 Polymer III 0.75 69.0610 Potato Flocculant Starch

[0205] Another series of retention and drainage tests is conducted likethe second series, with the PDD. The conditions and material are thesame as employed for previous series, except that the drainage aids areas follows: Polymer III of the invention and Polyflex CP.3, as discussedherein; Polymer M, a commercially available high MW polyacrylamideemulsion flocculant; and bentonite clay.

[0206] The polymeric materials are evaluated at 0.5, 0.75, and 1.0lbs./ton active polymer, while the bentonite clay is evaluated at 2, 4,and 6 lbs./ton, in accordance with typically utilized mill dosagelevels. The results are set forth in Table 9.

[0207] The Table 9 data illustrates the activity of the polymer of theinvention. Polyflex CP.3, bentonite clay, and Polymer III all exhibitpositive dose response activity, while Polymer M is not dosage active.The Polymer III provides equal to greater retention and drainageactivity as compared with bentonite clay.

[0208] Further as to the comparative activity shown in Table 9, PolymerM provides retention and drainage equal to that of Polymer III, but atdistinctly higher PEVR; this reduction in sheet uniformity/formation atequal drainage is undesirable. The drainage activity of Polymer IIIapproaches that of Polyflex CP.3, as 1.0 lb./ton of Polymer IIIapproaches the drainage of 0.5 lb. /ton Polyflex CP.3. It is again notedthat at these equal drainage times, the PEVR of the polymer of theinvention is lower than that of Polyflex CP.3, which is an indication ofimproved sheet uniformity or formation. TABLE 9 10 Lbs/Ton CationicPotato Vacuum Starch + 5 Lbs./Ton Aluminum % First Gravity DrainageDrainage Sulfate − 0.5 Lbs/Ton Pass Time - seconds VACUUM PEAK Peak toTime - seconds CPAM-P Flocculant + DOSAGE Fines (mass Equilibrium VACUUMEquilibrium (Vacuum Drainage Aid (Lbs/T) Retention measurement) (in Hg)(in Hg) Vacuum Ratio Time) None 0 87 60% 3 37 3 42 4 97 1 455 0 880Polyflex CP 3 0 5 96 42% 3 17 2 77 4 05 1 465 0 627 Polyflex CP 3 0 7598 81% 3 30 2 61 3 84 1 472 0 577 Polyflex CP 3 1 97 65% 3 18 2.49 3 701 486 0 515 Polymer III 0.5 95 39% 3 28 3 00 4 32 1 440 0 672 PolymerIII 0 75 86 26% 3 09 2.98 4 29 1 442 0 662 Polymer III 1 95 54% 3 092.91 4 22 1 451 0 649 Polymer M 0 5 95 27% 3 32 2 91 4 33 1 487 0 662Polymer M 0 75 95 80% 3 22 2.74 4 18 1 523 0 649 Polymer M 1 96.23% 3 382.71 4.29 1 583 0 651 Bentonite Clay 2 89 95% 3.32 3 25 4 51 1 391 0 724Bentonite Clay 4 93 96% 3 11 3.08 4.38 1 420 0 678 Bentonite Clay 6 9647% 4 61 2.96 4 21 1 423 0 649

[0209] Another series of Britt jar retention and CSF drainage tests isconducted with Polymer III and Polyflex CP.3, that utilizes higherlevels of CPAM-P flocculant and an additional flocculant, polyvinylamine(PVAm). The PVAm is produced via aqueous solution polymerization ofN-vinylformamide monomer, then with a subsequent hydrolysis of thepolymer to produce N-vinylamine. The subject polymer is hydrolyzed at90%, such that the resultant copolymer is 90 mole % N-vinylamine/10 mole% N-vinylformamide; the polymer is at 5% solids and exhibits anintrinsic viscosity in 1 M NaCl of 3 dL/g. The data in Table 10demonstrates the utility of the HAP at higher levels of CPAM-Pflocculant, and activity with a PVAm flocculant. TABLE 10 lbs/tonlbs/ton lbs/ton Drainage lbs/ton Avg Add #1 (active) Add #2 (active) Add#3 (active) Aid (active) Ret CSF Cationic 10 Alum 5 CPAM-P 0.5 none 0 536 370 Potato Flocculant Starch Cationic 10 Alum 5 CPAM-P 0 5 Polyflex CP3 0 75 78 6 650 Potato Flocculant Starch Cationic 10 Alum 5 CPAM-P 0 5Polymer III 0 75 70 8 595 Potato Flocculant Starch Cationic 10 Alum 5CPAM-P 1 none 0 66 6 395 Potato Flocculant Starch Cationic 10 Alum 5CPAM-P 1 Polyflex CP 3 0 75 91 6 680 Potato Flocculant Starch Cationic10 Alum 5 CPAM-P 1 Polymer III 0 75 80 9 610 Potato Flocculant StarchCationic 10 Alum 5 PV Am 0 5 none 0 35 9 435 Potato Flocculant StarchCationic 10 Alum 5 PV Am 0 5 Polyflex CP.3 0 75 91 1 730 PotatoFlocculant Starch Cationic 10 Alum 5 PV Am 0 5 Polymer III 0 75 74 0 665Potato Flocculant Starch

[0210] Another series of PDD experiments is conducted as presented inTable 11 under the procedures described previously, with Polymer III,Polyflex CP.3, and two additional Polyflex products, Polyflex CS andPolyflex CP.2, also available from Cytec Industries, Inc. The data inTable 11 demonstrates that the inventive Polymer III provides improvedretention and drainage activity compared to Polyflex CP.2, equivalentactivity as Polyflex CS, and activity approaching Polyflex CP.3. TABLE11 10 Lbs./Ton Cationic Potato % First Vacuum Starch + 5 Pass VACUUMPEAK Peak to Drainage Lbs/Ton 0.5 Lbs/Ton CPAM-P lbs/ton Fines GravityDrainage Equilibrium VACUUM Equilibrium Time - Flocculant + Drainage Aid(Active) Retention Time - seconds (in Hg) (in Hg) Vacuum Ratio secondsNone 0 85.2% 3 44 3 61 5 41 1 50 1 15 Polyflex CP 3 0 5 92 6% 3 12 2 774 28 1 55 0 64 Polyflex CP 3 0.75 94 1% 3 09 2.52 3 97 1 58 0 55 PolymerCP 3 1 93 5% 3 00 2 44 3 79 1 55 0 54 Polyflex CS 0 5 91 6% 3.12 3 20 475 1 48 0 75 Polyflex CS 0 75 92 8% 3 13 3 07 4 61 1 50 0 72 Polyflex CS1 95.9% 3 20 2 92 4 47 1 53 0 67 Polyflex CP 2 0.5 91 6% 3 16 3 33 4 781 43 0 75 Polyflex CP 2 0 75 92 7% 3 16 3 27 4 73 1 45 0 77 Polyflex CP2 1 91 2% 3 27 3 39 4 75 1 40 0 75 Polymer III 0 5 89 5% 3 35 3 30 4 771 44 0 80 Polymer III 0 75 94 0% 3 11 3 07 4 64 1 51 0 73 Polymer III 100 94.3% 3.13 3 01 4 57 1 52 0 68 Polymer E 0 5 91 9% 3 14 2 97 4 60 155 0 70 Polymer E 0.75 95 4% 3 08 2 75 4.54 1 65 0 70 Polymer E 1 92.9%3 20 2.66 4 60 1 73 0 75

[0211] A series of Britt jar retention and CSF drainage studies isconducted with the brine dispersion polymers described previously. Thesestudies set forth in Table 12 are conducted with Polymers IX and X,polymers of the inventive method modified with lauryl methacrylate;Polymers XI and XII, polymers of the inventive method modified withlauryl acrylate; Polymer VIII is the control polymer, produced underequivalent conditions as the hydrophobically associated polymers, butdoes not contain the hydrophobic substitution; Polyflex CP.3, andPolymer A, a conventional high MW anionic polyacrylamide powderflocculant. The test conditions and associated additives are as thosedescribed before, with the exception of the cationic flocculent utilizedbeing CPAM-N; this material is equivalent in composition and physicalform as the previously utilized CPAM-P. An anionic polyacrylamideflocculant (APAM) is also utilized. This material is a 30 mole % sodiumacrylate/70 mole % acrylamide copolymer, commercially available as aself-inverting emulsion. The data in Table 12 demonstrates the improvedactivity of the inventive material. Polymers IX and XI demonstrate highretention and drainage activity compared to commercial drainage aidbentonite clay, the control Polymer VIII, and the conventionalflocculant Polymer A. This improved activity is observed when utilizedwith a CPAM flocculent, with an APAM flocculant, and without aflocculant. TABLE 12 lbs/ton lbs/ton lbs/ton Drainage lbs/ton Avg CSFAdd #1 (active) Add #2 (active) Add #3 (active) Aid (active) RetDrainage Cationic 10 Alum 5 CPAM-N 0 5 None 0 53 6 370 Potato FlocculantStarch Cationic 10 Alum 5 CPAM-N 0 5 Polymer VIII 0 75 71 1 620 PotatoFlocculant Starch Cationic 10 Alum 5 CPAM-N 0 5 Polymer IX 0 75 78 9 650Potato Flocculant Starch Cationic 10 Alum 5 CPAM-N 0 5 Polymer XI 0 7576 4 640 Potato Flocculant Starch Cationic 10 Alum 5 CPAM-N 0 5 PolymerX 0 75 73 1 630 Potato Flocculant Starch Cationic 10 Alum 5 CPAM-N 0 5Polymer XII 0 75 555 Potato Flocculant Starch Cationic 10 Alum 5 CPAM-N0.5 Polyflex CP 3 0.75 86 0 680 Potato Flocculant Starch Cationic 10Alum 5 CPAM-N 0 5 Polymer A 0 75 68 1 620 Potato Flocculant StarchCationic 10 Alum 5 CPAM-N 0 5 Bentolite HS 4 70 7 630 Potato FlocculantStarch Cationic 10 Alum 5 None 0 Polymer VIII 0 5 59 6 560 Potato StarchCationic 10 Alum 5 None 0 Polymer IX 0 5 66.0 545 Potato Starch Cationic10 Alum 5 None 0 Polymer XI 0 5 67 8 555 Potato Starch Cationic 10 Alum5 None 0 Polymer X 0 5 52 0 495 Potato Starch Cationic 10 Alum 5 None 0Polymer XII 0 5 435 Potato Starch Cationic 10 Alum 5 None 0 Polyflex CP3 0 5 71 5 585 Potato Starch Cationic 10 Alum 5 None 0 Polymer A 0 5 571 560 Potato Starch Cationic 10 Alum 5 APAM 0 5 Polymer VIII 0 5 530Potato Flocculant Starch Cationic 10 Alum 5 APAM 0 5 Polymer IX 0 5 565Potato Flocculant Starch Cationic 10 Alum 5 APAM 0 5 Polymer XI 0 5 540Potato Flocculant Starch Cationic 10 Alum 5 APAM 0 5 Polymer X 0 5 540Potato Flocculant Starch Cationic 10 Alum 5 APAM 0.5 Polymer XII 0 5 520Potato Flocculant Starch Cationic 10 Alum 5 APAM 0 5 Polyflex CP 3 0 5630 Potato Flocculant Starch Cationic 10 Alum 5 APAM 0 5 Polymer A 0 5505 Potato Flocculant Starch

[0212] A series of evaluations is conducted on the PDD, utilizingequivalent methods as described in Table 12. The studies set forth inTable 13 are conducted with Polymers IX and X, polymers of the inventivemethod modified with lauryl methacrylate; Polymers XI and XII, polymersof the inventive method modified with lauryl acrylate; Polymer VII isthe control polymer, produced under equivalent conditions as thehydrophobically associated polymers, but does not contain thehydrophobic substitution; and Polyflex CP.3. The data in Table 13demonstrates positive drainage activity for Polymers IX, X, and XIcompared to the unmodified control Polymer VIII. The Polymers IX, X, andXI also indicate a positive dosage response at low PEVR, while theunmodified control does not demonstrate a remarkable dosage response.TABLE 13 10 lbs/ton Cat Potato Starch + 5 % First Vacuum lbs/lon 0 5lbs/ton Pass VACUUM PEAK Peak to Drainage CPAM-N Flocculant + lbs/tonFines Gravity Drainage Equilibrium VACUUM Equilibrium Time- Drainage Aid(Active) Retention Time - seconds (in Hg) (in Hg) Vacuum Ratio secondsNone 86.1% 3.98 3 33 5 11 1 53 0 94 Polymer VIII 0 5 93 1% 3 76 2 89 438 1 52 0 67 Polymer VIII 1 95 6% 3 79 2.72 4 18 1.54 0 63 Polymer IX 05 93 7% 3 71 2 77 4 12 1 49 0 64 Polymer IX 1 94 5% 3.64 2.51 3 75 1 500 54 Polymer X 0 5 92.5% 3 69 2 79 4 12 1 48 0 65 Polymer X 1 97 2% 3 662 48 3 72 1 50 0 55 Polymer XI 0 5 94 0% 3 65 2.74 4 07 1 49 0 62Polymer XI 1 93 7% 3 68 2.49 3 87 1 55 0 54 Polymer XII 0 5 86.0% 3 863.23 4 69 1.45 0 77 Polymer XII 1 89 1% 3 73 3 00 4 43 1 47 0 71Polyflex CP 3 0 5 95 8% 3 70 2 60 3 93 1 51 0 57 Polyflex CP.3 1 94 9% 355 2.29 3 52 1 54 0 49

[0213] It is noted that the foregoing examples have been provided merelyfor the purpose of explanation and are in no way to be construed aslimiting of the present invention. While the present invention has beendescribed with reference to an exemplary embodiment, it is understoodthat the words which have been used herein are words of description andillustration, rather than words of limitation. Changes may be made,within the purview of the appended claims, as presently stated and asamended, without departing from the scope and spirit of the presentinvention in its aspects. Although the present invention has beendescribed herein with reference to particular means, materials andembodiments, the present invention is not intended to be limited to theparticulars disclosed herein; rather, the present invention extends toall functionally equivalent structures, methods and uses, such as arewithin the scope of the appended claims.

1. A method of making a cellulosic fiber composition which comprises adding, to a cellulosic pulp slurry, a hydrophobically associative polymer comprised of reccurring units of least one hydrophobic ethylenically unsaturated monomer present in an amount from about 0.001 mole percent to about 10 mole percent, and recurring units of at least one monomer selected from a nonionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer, or an anionic ethylenically unsaturated monomer, with the proviso that the at least one hydrophobic ethylenically unsaturated monomer does not contain 2,4,6-triphenoethyl benzene.
 2. The method of claim 1 wherein the hydrophobic ethylenically unsaturated monomer comprises an ethylenically unsaturated monomer having at least one pendant hydrophobic group.
 3. The method of claim 2 wherein the pendant hydrophobic group is selected from one or more of C₄ to C₂₀ alkyls, C₄ to C₂₀ cycloalkyls, polynuclear aromatic hydrocarbon groups, alkaryls wherein alkyl has one or more carbons; haloalkyls of four or more carbons, or polyalkyleneoxy groups.
 4. The method of claim 3 wherein the hydrophobic group is selected from one or more of C₄-C₂₀ alkyl groups.
 5. The method of claim 3 wherein the hydrophobic group is selected from one or more of C₈-C₂₀ alkyl groups.
 6. The method of claim 1 wherein the hydrophobic ethylenically unsaturated monomer is selected from one or more hydrocarbon esters of ethylenically unsaturated carboxylic acids and their salts.
 7. The method of claim 1 wherein the hydrophobic ethylenically unsaturated monomer is selected from one or more of the C₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid.
 8. The method of claim 1 wherein the nonionic ethylenically unsaturated monomer is selected from one or more of acrylamide, methacrylamide, N-alkylacrylamides, N,N-dialkylacrylamides, methyl acrylate, methyl methacrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, or N-vinyl pyrrolidone.
 9. The method of claim 8 wherein the N-alkylacrylamide is N-methylacrylamide.
 10. The method of making the cellulosic fiber composition of claim 8 wherein the at least one nonionic ethylenically unsaturated monomer is selected from one or more of acrylamide, methacrylamide, or N-alkylacrylamides.
 11. The method of making the cellulosic fiber composition of claim 8 wherein the at least one nonionic ethylenically unsaturated monomer is acrylamide.
 12. The method of making the cellulosic fiber composition of claim 1 wherein the at least one anionic ethylenically unsaturated monomer is selected from one or more of acrylic acid, methylacrylic acid, 2-acrylamido-2-methyl-propane sulfonate, sulfoethyl-(meth)acrylate, vinylsulfonic acid, styrene sulfonic acid, maleic acid or the salts thereof.
 13. The method of making the cellulosic fiber composition of claim 12 wherein the at least one anionic ethylenically unsaturated monomer is selected from one or more of acrylic acid, methacrylic acid or the salts thereof.
 14. The method of making the cellulosic fiber composition of claim 13 wherein the at least one anionic ethylenically unsaturated monomer is selected from one or more of the sodium or ammonium salts of acrylic acid.
 15. The method of making the cellulosic fiber composition of claim 1 wherein the at least one hydrophobic ethylenically unsaturated monomer groups is present in an amount from about 0.01 mole percent to about 1 mole percent.
 16. A method of making a cellulosic fiber composition which comprises adding, to a cellulosic pulp slurry, a water soluble hydrophobically associative polymer comprising: recurring units of at least one hydrophobic ethylenically unsaturated monomer present in an amount from about 0.001 mole percent to about 10 mole percent and selected from one or more of C₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid; recurring units of at least one nonionic ethylenically unsaturated monomer is selected from one or more of acrylamide, methacrylamide, N-alkylacrylamides, N,N-dialkylacrylamides, methyl acrylate, methyl methacrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, or N-vinyl pyrrolidone; recurring units of at least one anionic ethylenically unsaturated monomer is selected from one or more of acrylic acid, methylacrylic acid, 2-acrylamido-2-methylpropane sulfonate, sulfoethyl-(meth)acrylate, vinylsulfonic acid, styrene sulfonic acid, maleic acid or the salts thereof.
 17. The method of making a cellulosic fiber composition of claim 16 wherein the water soluble hydrophobically associative polymer comprises: recurring units of at least one hydrophobic ethylenically unsaturated monomer present in an amount from about 0.001 mole percent to about 10 mole percent and selected from one or more of C₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid; recurring units of at least one nonionic ethylenically unsaturated monomer selected from one or more of acrylamide, methacrylamide, or N-alkylacrylamides; recurring units of at least one anionic ethylenically unsaturated monomer is selected from one or more of acrylic acid, methacrylic acid or the salts thereof.
 18. A method of making a cellulosic fiber composition which comprises adding, to a cellulosic pulp slurry, a water soluble hydrophobically associative anionic polymer comprising at least one hydrophobic ethylenically unsaturated monomer selected from one or more of lauryl acrylate or lauryl methacrylate, acrylamide, and acrylic acid.
 19. The method of claim 18 wherein the hydrophobic ethylenically unsaturated monomer is lauryl acrylate.
 20. The method of claim 18 wherein the hydrophobic ethylenically unsaturated monomer is lauryl methacrylate.
 21. A cellulosic fiber composition comprising an aqueous slurry of cellulosic pulp and a water soluble hydrophobically associative polymer, wherein the polymer comprises: recurring units of at least one hydrophobic ethylenically unsaturated monomer present in an amount from about 0.001 mole percent to about 10 mole percent, and recurring units of at least one monomer selected from a nonionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer, or an anionic ethylenically unsaturated monomer, with the proviso that the at least one hydrophobic ethylenically unsaturated monomer does not contain 2,4,6-triphenoethyl benzene.
 22. The cellulosic fiber composition of claim 21 wherein the at least one hydrophobic ethylenically unsaturated monomer comprises an ethylenically unsaturated monomer having at least one pendant hydrophobic group.
 23. The cellulosic fiber composition of claim 22 wherein the pendant hydrophobic group is selected from one or more of C₄ to C₂₀ alkyls, C₄ to C₂₀ cycloalkyls, polynuclear aromatic hydrocarbon groups, alkaryls wherein alkyl has one or more carbons; haloalkyls of four or more carbons, or polyalkyleneoxy groups.
 24. The cellulosic fiber composition of claim 23 wherein the at least one hydrophobic group is selected from one or more of C₄-C₂₀ alkyl groups.
 25. The cellulosic fiber composition of claim 24 wherein the at least one hydrophobic group is selected from one or more of C₈-C₂₀ alkyl groups.
 26. The cellulosic fiber composition of claim 21 wherein the at least one hydrophobic ethylenically unsaturated monomer is selected from one or more hydrocarbon esters of ethylenically unsaturated carboxylic acids and their salts.
 27. The cellulosic fiber composition of claim 26 wherein the at least one hydrophobic ethylenically unsaturated monomer is selected from one or more of the C₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid.
 28. The cellulosic fiber composition of claim 21 wherein the at least one nonionic ethylenically unsaturated monomer is selected from one or more of acrylamide, methacrylamide, N-alkylacrylamides, N,N-dialkylacrylamides, methyl acrylate, methyl methacrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, or N-vinyl pyrrolidone.
 29. The cellulosic fiber composition of claim 28 wherein the at least one nonionic ethylenically unsaturated monomer is acrylamide.
 30. The cellulosic fiber composition of claim 21 wherein the at least one anionic ethylenically unsaturated monomer is selected from one or more of acrylic acid, methylacrylic acid, 2-acrylamido-2-methyl-propane sulfonate, sulfoethyl-(meth)acrylate, vinylsulfonic acid, styrene sulfonic acid, maleic acid or the salts thereof.
 31. The cellulosic fiber composition of claim 30 wherein the at least one anionic ethylenically unsaturated monomer is selected from one or more of the sodium or ammonium salts of acrylic acid.
 32. The cellulosic fiber composition of claim 21 wherein the at least one hydrophobic ethylenically unsaturated monomer groups is present in an amount from about 0.01 mole percent to about 1 mole percent.
 33. A cellulosic fiber composition comprising an aqueous slurry of cellulosic pulp and a water soluble hydrophobically associative polymer wherein the polymer comprises: recurring units of at least one hydrophobic ethylenically unsaturated monomer present in an amount from about 0.001 mole percent to about 10 mole percent and selected from one or more of C₁₀-C₂₀ alkyl esters of acrylic and methacrylic acid; recurring units of at least one nonionic ethylenically unsaturated monomer is selected from one or more of acrylamide, methacrylamide, N-alkylacrylamides, N,N-dialkylacrylamides, methyl acrylate, methyl methacrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, or N-vinyl pyrrolidone; recurring units of at least one anionic ethylenically unsaturated monomer is selected from one or more of acrylic acid, methylacrylic acid, 2-acrylamido-2-methyl-propane sulfonate, sulfoethyl-(meth)acrylate, vinylsulfonic acid, styrene sulfonic acid, maleic acid or the salts thereof.
 34. The cellulosic fiber composition of claim 33 wherein the water soluble hydrophobically associative polymer comprises: at least one hydrophobic ethylenically unsaturated monomer selected from one or more of dodecyl acrylate or dodecyl methacrylate, the at least one nonionic ethylenically unsaturated monomer is acrylamide, the at least one anionic ethylenically unsaturated monomer is selected from one or more of the sodium or ammonium salts of acrylic acid.
 35. The cellulosic sheet of claim 33 comprising paper.
 36. A cellulosic fiber composition comprising an aqueous slurry of cellulosic pulp and a water soluble hydrophobically associative polymer wherein the polymer comprises: recurring units of a hydrophobic ethylenically unsaturated monomer selected from one or more of lauryl acrylate or lauryl methacrylate, recurring units of a nonionic ethylenically unsaturated monomer is acrylamide, and recurring units of an anionic ethylenically unsaturated monomer is acrylic acid.
 37. The cellulosic sheet of claim 36 comprising paper. 